Laser ARPES Studies of Cuprate High Temperature Superconductors

When: Wednesday, November 06, 2013 at 3:00 pm
Where: DA 114
Speaker: Inna Vishik
Organization: MIT
Sponsor: Condensed Matter Seminar

Angle-resolved photoemission spectroscopy (ARPES) measures electronic structure in momentum-space and is a powerful tool for investigating quantum materials, including the high-temperature superconducting cuprates.  The microscopic mechanism of cuprate superconductivity remains unresolved, but ARPES has made many contributions to our understanding of these compounds, including helping to elucidate the superconducting order parameter.   A recent development in the technique involves using a narrow-bandwidth UV laser as a light source, and the superior resolution of laser-ARPES provides unprecedented access to the lowest lying excitations relevant to ground state properties.  I will present two studies demonstrating the capabilities of this technique to reveal new cuprate physics, particularly when combined with a comprehensive doping-dependence study.  The first focuses on a dispersion anomaly in the cuprates that was first discovered by laser-ARPES and has implications for interpreting thermodynamic experiments.  The second study looks at the momentum and doping dependence of spectral gaps in the superconducting state.  It is found that the gap phenomenology changes abruptly at two dopings, giving spectroscopic evidence for three distinct quantum phases inside the superconducting dome.  Interpretations and implications will be discussed.

References:

I. M. Vishik, M. Hashimoto, R.-H. He, W. S. Lee, F. Schmitt, D. H. Lu, R. G. Moore, C. Zhang, W. Meevasana, T. Sasagawa, S. Uchida, K. Fujita, S. Ishida, M. Ishikado, Y. Yoshida, H. Eisaki, Z. Hussain, T. P. Devereaux, and Z.-X. Shen, “Phase competition in trisected superconducting dome,” Proc. Natl. Acad. Sci. 109 (45) 18332-18337 (2012).

I. M. Vishik, W. S. Lee, F. Schmitt, B. Moritz, T. Sasagawa, S. Uchida, K. Fujita, S. Ishida, C. Zhang, T. P. Devereaux, and Z. X. Shen, “Doping-Dependent Nodal Fermi Velocity of the High-Temperature Superconductor Bi2Sr2CaCu2O8+δ Revealed Using High-Resolution Angle-Resolved Photoemission Spectroscopy,” Phys. Rev. Lett. 104, 207002 (2010).

Host: Assistant Professor Adrian Feguin